The present invention relates generally to automotive, industrial, and commercial parts cleaning, and, more particularly, to improved formulations for increasing the effectiveness and recyclability of cleaning solvents.
In industry today, there has been an increasing awareness of the importance of washing mechanical parts. In almost every repair, reconstruction, and rebuilding of motors, engines, and/or machines, it is necessary to clean oily, greasy, or otherwise dirty or contaminated parts before they can be repaired and reassembled. Further, in a number of cases, machining and refabricating operations, particularly those carried out on metal parts, leave residues or contaminants which are desirably cleaned before the part or component in question is reassembled or otherwise the subject of a completed operation.
In most cases, the kind of dirt and contamination which has accumulated on metal parts is that of an oily, greasy residue. In the case of automotive, truck, agricultural, and earth-moving construction machinery components, the parts in question gradually become covered with oil or grease that has leaked from the crankcases or gear housings of the machines, and these in turn attract dust, sand, dirt, and other constituents of the environment in which they work. Almost all oils and greases have the capability not only of attracting dust and dirt, but also, in effect, of acting as an adhesive for these and other contaminants.
Normally, for reasons of rust prevention, and particularly for reasons of solubility, such parts, being possessed of an oily, greasy residue, are best cleaned using hydrocarbon-based solvent systems rather than aqueous systems. The use of aqueous systems calls for using large quantities of water and requires emulsifying the oil and grease that is, in effect, serving as a dirt binder. Such cleaning, while effective if conducted properly, involves time-consuming washing/emulsification/saponification steps followed by rinsing and subsequent application of a corrosion inhibitor coating. In addition, disposing of oil-containing residues is sometimes subject to prohibition or regulation.
Accordingly, rather than pursue this method, most parts are simply washed in a hydrocarbon-based solvent that is compatible with the oils and greases in question, and which therefore serves to remove the dirt quite rapidly and effectively. This is particularly true when combined with a scrubbing or mechanical agitation action, i.e., brushing or dipping and agitating of parts, or both. Where the solvent is confined to a recirculating washer, the solvent can be retained and collected for recycling so as not to require being disposed of in violation of environmental regulations.
In connection with the use of hydrocarbon-based solvents, certain problems arise. These include environmental and fire hazard concerns, one consequence of which has been the increasing use of relatively high flash point solvents. In many cases, these solvents used have a flash point of 100.degree. F. or above and are primarily aliphatic in nature with a certain aromatic constituent. Newer solvents have a 150.degree. F. or higher flash point and are predominantly or almost exclusively aliphatic.
Referring to the equipment used in parts washing, while simple dip tanks have been known to be used with some effectiveness, the most cost- and labor-effective method of small-scale parts washing, (i.e., that carried on in maintenance, repair, and rebuild shops and garages and industrial fabrication and assembly facilities of all sizes), has been to use parts washers which include a sink or the like positioned atop a reservoir of hydrocarbon-based solvent and wherein this solvent is circulated from the reservoir though a pump and directed over the parts being cleaned from a nozzle at the end of a conduit or the like. Parts washers using such hydrocarbon-based solvents include those of the general type described in U.S. Pat. No. 3,522,814, of which many hundreds of thousands have been sold and/or are in use.
Referring again to automotive, industrial, and commercial parts washing, when the cost of hydrocarbon-based solvent was very low and the regulatory atmosphere was somewhat lax, it was not uncommon to provide a rather crude filter to be used with such solvent and for the solvent to be changed by a route or serviceman every two to four weeks. The used solvent would be picked up by the route man, who then furnished a charge of new solvent for the parts washer. This cycle would commonly be repeated on a two to twelve week cycle or as needed.
When hydrocarbon-based solvent prices were low, this was an economical, common sense approach to parts washing problems. The combination of the relatively crude filter and simple gravity settling provided a gross separation of contaminants which was satisfactory for the times in question. Now, however, hydrocarbon-based solvent costs are much higher, and environmental regulations are such that it is much more desirable to ensure maximum use and re-use of a particular charge of solvent. However, this desirable state of affairs has not heretofore been able to be fully achieved in practice.
One characteristic of parts washer solvent that has been subjected to even comparatively few washing cycles is that the dirt entrained therein includes finely dispersed particles, many of which may be of sub-micron size. While sand, gravel, metal filings, and the like cleaned from dirty or greasy parts rapidly settle out, a significant portion of the contaminants in solvent used for parts washing is comprised of very fine particles that are resistant to settling. As a result, while the solvent's cleaning effectiveness may not be impaired, due to the dispersed and unsettled contamination, it may be difficult to determine visually that the solvent can still be used effectively. Consequently, such solvent may be changed more often than needed.
If it were possible to achieve a greater separation of dirt and particles from the mass of solvent within a finite time, say fifteen minutes to one hour, the effectiveness and useful lifetime of much parts cleaning solvent would be greatly increased. It is possible that, by positioning the liquid pump inlet an appropriate distance from the bottom of the reservoir, if there were highly effective gravity separation of contaminants, the pump could continue to circulate comparatively clean solvent, while the case, the contaminants would continue to self-separate by gravity. Thus, the supernatant liquid within the reservoir would remain clean and be able to be used over a much longer period of time.
In speaking of reclamation of hydrocarbon solvents, being that the current regulatory atmosphere in some ways promotes this practice, when recycling of the hydrocarbon-based solvent used in parts cleaning is called for, i.e., by filtration, distillation of the solvent at a recycle center, and/or by various other commonly known methods, an economic price is extracted both for recycling very dirty solvent and also for distilling solvent that has sufficient solids suspended so as to be of reduced effectiveness in use as a cleaning material.
If it were the case that a greater separation of the dirt and particles in used or spent hydrocarbon-based solvent could be achieved, recycling would be simplified in that the major portion of the contaminants could be removed into a contaminant-rich layer by physical separation, thus reducing the accumulation of sludge in the distillation phase of recycling. Heat transfer would be better and equipment damage would be minimized if the solvent that was ultimately recycled by distillation were cleaner when entering the distillation phase of recycling.
While it is not known with certainty all the reasons why the contaminants in parts cleaning hydrocarbon-based solvent are apparently so highly resistant to gravity separation, it is known that modern motor oil, cutting and machining fluids, and grease formulations include detergent/dispersant additives which form a part of the dirt and grime which accumulates on mechanical parts, both inside and outside sealed machine areas. The detergent/dispersant additives remaining in these oil, fluid, and grease residues may serve to suspend fine contaminants within the cleaning solvent and prevent their separation by gravity or filtration.
A drawback with the concept of adding certain performance enhancing products to solvent for the purpose of separating therefrom suspended, fine-particle-size contaminants has been that of expense of the additive. Hence, since the main incentive to clarify solvents used in parts washing application is to economize on the use of solvent, primarily by creating particle separation that enables the supernatant layer of the solvent to be used for longer periods of time, if such a process involves considerable effort and expense, then it cannot be economically justified.
Moreover, if any treatment is such that it renders ineffective a primary requirement of the solvent, namely, that it be able to be recycled, then such additives or modifying compositions would be seriously disadvantageous. Accordingly, if a relatively persistent additive were able to be found, such an additive would have economic advantages in that it would be able to be used for a significant period of time.
Moreover, if an additive available which would not only be persistent in use, but which would remain in a solvent composition to and through a recycling phase, then such a composition would have an extremely important economic and ecological advantages.
In view of the inability of the prior art to have developed an additive composition for a cleaning solvent, particularly a parts washing solvent, which additive would be highly persistent in use, and might even survive recycling by distillation, an object of the present invention is to provide an improved petroleum or other solvent composition that includes a durable or persistent component that also aids contaminant particle separation.
A further object of the invention is to provide a solvent which will provide a combination of properties, namely, the ability to impart rapid agglomeration of dispersed fine particles in the solvent and which would survive recycling by distillation.
A further object of the invention to provide an enhanced solvent that greatly accelerates dirt and particle separation and remains effective after solvent reclamation and/or solvent recycling has been conducted by various methods, including distillation.
A still further object of the invention is to provide an enhanced solvent and/or solvent additive that facilitates easier initial separation of contaminants for more efficient and cost effective recycling, especially wherein the additive largely remains in a solvent supernatant layer rather than separately with agglomerated contaminants.
Another object of the invention is to provide a modified composition wherein a single additive, or combination of related additives, will serve to perform a solvent clarifying function in respect to fine particles and which additive will further remain present in the solvent during repeated distillative recycling.
Yet another object of the present invention is to provide a composition which, when added to a cleaning solvent, is compatible with other additives such as settling accelerants, as well as with impurities or other contaminants finding their way into parts washing solvent.
Another object of the invention is to provide a persistent additive for a solvent, which additive is effective in the presence of certain limited amounts of water and whose performance in some cases is enhanced by the presence of small portions of water.
A further object of the invention is to provide a composition which will form an azeotrope or constant boiling mixture with a range of solvent compositions so as to remain with solvent being distilled rather than being separated therefrom by distillation.
Yet another object is to provide a method of providing improved solvent performance, which method comprises treating cleaning solvent with an additive which will extend its service life, thereafter distilling the solvent after use to separate therefrom high boiling residues, and repeating this process periodically, occasionally adding a slight additional amount of the additive sufficient to return the solvent composition to its original specification.
Another object of the invention is to provide an additive which is compatible with and not harmful to equipment used in distillative recycling.
The foregoing and other advantages of the invention are achieved in practice by providing a solvent processing method which comprises adding to a body of solvent a treating composition comprising an active ingredient selected from the group consisting of C.sub.14 and lower alcohols, C.sub.14 and lower diols, C.sub.14 and lower polyols, C.sub.14 and lower glycol ethers, and mixtures of said alcohols, diols, polyols and glycol ethers, preferably of the C.sub.6 -C.sub.8 variety, utilizing the solvent in a parts washing operation and periodically distilling the same to remove impurities, and, following distillation, determining the effective level of such additive in the composition, and periodically adding small amounts of said composition until the solvent composition has reached its original specification.
The manner which the foregoing objects and advantages of the invention are achieved in practice will become more clearly apparent when reference is made to the preferred manner of practicing the invention, as reflected in the examples set out below.